This invention relates to archery bows and accessories thereof, and more particularly to a damping device or devices to be incorporated into a bow handle to absorb excess energy thereby reducing hand shock, noise and bow vibration.
Most everyone is familiar with the archery bow and arrow. The bow is a rather simple mechanical device used to store energy derived from the archer during the drawing of the bow and then when the archer looses the bow string the bows energy is rapidly released. The greater portion of this energy goes into the launching of the arrow and most of the remainder finds its way back into the bow with the excess resulting in noise or simply lost in the transfer process. Some of the energy that goes back into the bow returns it to its original undrawn state but much of it goes into moving various bow components resulting in bow hand shock and system vibrations.
Over the years archery manufactures have attempted to make the bow more efficient and in some ways they have succeeded. The compound bow is an example of the modem manufactures success in being able to increase the amount of energy that a bow can store, some modem compound bows store almost 50% more energy per peak pound of draw weight as did the longbows of years past. The basic premise being that the more energy stored the more energy one has available to launch the arrow and the result will be greater and greater arrow launch velocities. To some extent this has become true and arrow initial velocities for bow hunters have increased over the last couple of decades. Along with bows that are capable of storing energy more efficiently, the quest for higher arrow velocities has been further augmented by the fact that lighter mass weight arrows have greater launch velocities than do heavier mass weight arrows. Arrow manufactures in the last two decades have taken advantage of the availability of higher strength materials and made lighter and lighter mass weight arrows available.
The result is that today's bows are storing more energy and are being used to launch lighter and lighter mass weight arrows. The problem arises from the fact that the amount of energy that a given bow can transfer to an arrow is directly proportional to the mass weight of the arrow being shot. The overall mechanical efficiency of the bow is determined in the usual fashion in that we look at the ratio of the energy coming out of the system divided by the energy that was put into the system. In this case we have the kinetic energy in the arrow at launch divided by the energy put into the bow by the archer prior to arrow launch. In this manner it is easily verifiable that bows in general can have efficiencies of nearly 90% when shooting very heavy mass weight arrows and the same bow can exhibit efficiencies in the lower 60 percentile when shooting very light mass weight arrows. The result is that a bow shooting heavy mass weight arrows imparts most of its stored energy to the arrow and after launch the bow must absorb only 10% of the original stored energy. On the other hand if the same bow were to shoot very light mass weight arrows it would have to absorb up to 40% of the original stored energy after each launch.
A number of the compound bows being offered today can store as much as 100 foot pounds of energy therefore it is conceivable that such a bow shooting a very light weight arrow could have to absorb up to almost 40 foot pounds of energy after each arrow launch. This excess energy trapped in the bow often results in a great deal of bow shock and vibration which is not only unpleasant to the archer but also takes its toll on the bows components and the accessories mounted to the bow.
Although some manufactures have tried to address the problem of this residual energy by using after market shock absorbing stabilizers and several patents have been issued for such devices (e.g. U.S. Pat. No. 5,016,602 and U.S. Pat. No. 5,411,009). These devices tend to be effective only along the axis on which they are mounted and the degree of damping that they provide is generally proportional to the amount of weight that they add to the system. The proposed damper is designed to be multi-axial in its ability to absorb and dissipate excess energy and in comparison it adds much less mass weight making it much more effective than previous dampers.